1. Field of the Invention
The present invention relates generally to hybridoma cell lines and, more particularly, to a hybridoma cell line that secretes a monoclonal antibody defining an epitope found on an antigen of the classification termed CEA/NCA (carcinoembryonic antigen/normal cross-reacting antigen).
Monoclonal antibodies (MoAbs) binding epitopes on tumor associated antigens are potent weapons in the ongoing fight against cancer. MoAbs belong to a broad classification of immunologically important compositions of matter called immunoglobulins, which include whole antibodies and active (binding) fragments thereof. For the most part, MoAbs are secreted by hybridoma cells which are produced by combining normal antibody-forming cells with immortal immune cells, such as myeloma cells.
Carcinoembryonic antigen is a cell surface antigen found on a variety of neoplasms, including forms of ovarian, colorectal and breast cancer. It is called CEA because it is present in high concentrations in embryonic cells but is repressed in adult cells. It occurs in low concentrations in normal tissue including breast and colorectal and in high concentrations in neoplastic cells probably because it is derepressed.
CEA is a large glycoprotein which has two antigenically distinct regions. The first is NCA (Normal Colon or Cross-reacting Antigen) which is shared in relatively high concentrations with a different protein present on a wide range of normal tissues (ex. colon, lung, breast). The second region (CEA) is antigenically distinct; therefore antibodies directed against this molecule can be differentiated into: 1) CEA only -- little cross-reacting with NCA; 2) CEA/NCA -- cross reacts with a wide range of normal tissues including granulocytes.
MoAbs find particular utility as the targeting moiety of immunotoxin and immunoimaging conjugates employed in the diagnosis and treatment of neoplasia. There is therefore an ongoing need for the development of novel hybridoma cell lines that secrete MoAbs defining epitopes on tumor associated antigens such as CEA/NCA.